there are sets of 2 and 3 digit numbers stamped on certain pieces, but those were to help assembly.

A camera made by Folmer Graflex Corp (1928-1944) would most certainly have a 6 digit number.

I have a 2D and it's hard to describe but look at the rear section of the camera. There is essentiall a box that holds the bellows that is held by two upright brass arms. To keep these arms together there is an interconnecting board that runs underneath the box.

Grab a flash light and look on this board. It's usualy best if you stand forward of the arms and look and the front/top of the board either right or left side.

this one's american, and yes, the rear standard doesn't swing as on a 2D but the serial number is in there some where

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1378591876
this one is in new Zeland and is from Kodak LTD, not Folmer Graflex. and even though the name is the same, it's a radically different camera. Since this was made in the UK I won't have info on this. Folmer Graflex, and Graflex Inc were made in Rochester, and I do have info on those.